JP2015163403A - Sand collecting method for sand sedimentation pond - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sand collecting method capable of letting earth accumulated on the bottom surface of a sand sedimentation pond efficiently flow without leaving near a side wall of the sand sedimentation pond, in a sand collecting device for the sand sedimentation pond, including a nozzle for letting earth accumulated on the bottom surface of the sand sedimentation pond flow by jetting low-pressure water from the nozzle.SOLUTION: A sand collecting method for a sand sedimentation pond includes jetting low-pressure water from a nozzle and letting earth accumulated on the bottom surface of the sand sedimentation pond flow into a trough provided on the bottom of the sand sedimentation pond. In more details, the method includes: jetting from the nozzle installed near the side wall of the sand sedimentation pond to the bottom surface of the sand sedimentation pond in a range of 30-60 degrees of an incident angle to the bottom surface; splitting water landing the bottom surface to the trough direction and the side wall direction on the bottom surface; and joining earth accumulated between an injection water landing point and the side wall with water split in the trough direction by water split to the side wall direction so as to let flow into the trough together with earth accumulated between the injection water landing point and the trough.

Description

  The present invention relates to a sand collection method for collecting sediment deposited in a sand basin of a sewage treatment facility in a sand collection pit by a low pressure sand collection method.

In the state where the water in the sedimentation basin was discharged by the drainage pump (drainage state), low pressure water of less than 3 kg / cm ² was jetted from the nozzle, and the sediment deposited on the bottom of the sedimentation basin was washed away. The low pressure sand collection system that collects in the sand collection pit and the sand removal device that pumps up the earth and sand collected in the sand collection pit together with water by the sand pump installed in the sand collection pit and transfers it to the sewage settling basin are patented. It is disclosed in Document 1.

  The nozzle near the side wall of the sand settling basin in the low pressure sand collecting type sand collecting device is a nozzle installed near the side wall of the settling basin for each region obtained by dividing the bottom surface of the sand settling basin into the direction of water flow in the settling basin. A plurality of headers are attached at equal intervals.

  By the way, the bottom surface of the sand basin has an inclination angle of 5-7 degrees with respect to a horizontal plane toward the bottom center of the sand basin. And as FIG. 15 shows, the nozzle 9b of the conventional nozzle header NH is attached so that the incident angle (theta) with respect to the bottom of the settling basin of the nozzle may be less than 45.

Japanese Patent No. 3315489

  The amount of sediment deposited on the bottom surface of the sand basin is the largest in the region near the side wall W of the bottom surface 2a. However, as described above, the nozzle 9b of the conventional nozzle header NH has an incident angle with respect to the bottom surface of the settling basin of less than 45 degrees. Therefore, the water sprayed from the nozzle and landing on the bottom surface of the settling basin Since everything flows to the trough 8a side, the earth and sand that effectively flows due to the water discharged from the nozzle is limited to the range on the trough 8a side from the landing position on the bottom of the settling basin of the water discharged from the nozzle, as shown in FIG. As shown in the figure, there is a problem that the earth and sand S having the largest amount of accumulation between the landing position and the side wall W may remain without being washed away.

  The present invention has been made in view of the above circumstances, in a sand collection device for a sand basin provided with a nozzle for injecting low-pressure water from a nozzle and flowing sediment deposited on the bottom of the sand basin, It is an object of the present invention to provide a sand collection method capable of efficiently flowing earth and sand accumulated on the bottom surface of a sand basin without remaining in the vicinity of the side wall of the sand basin.

  In order to achieve the above object, the present invention provides a sand collection method for a sand basin in which low pressure water is jetted from a nozzle and the earth and sand accumulated on the bottom surface of the sand basin is passed through a trough provided at the bottom of the sand basin. The nozzle installed near the side wall is sprayed onto the bottom surface of the sand basin with an incident angle with respect to the bottom surface in the range of 30 to 60 degrees, and the water landing on the bottom surface is shunted in the trough direction and the side wall direction on the bottom surface. The sand that has accumulated between the jetting point and the sidewall is merged with the water that is diverted in the trough direction, and flows into the trough together with the sediment that has accumulated from the jetting point to the trough. It is characterized by that.

  When the incident angle of the nozzle to the bottom of the sand basin is set in the range of 30 to 60 degrees, the water sprayed from the nozzle and landing on the bottom of the sand basin is divided into the trough direction and the side wall direction on the bottom surface. . As the incident angle is smaller, the trough direction flow rate increases and the side wall direction flow rate decreases. Conversely, the larger the incident angle, the smaller the flow in the trough direction and the higher the flow in the side wall direction. Therefore, the incident angle of the nozzle water discharge with respect to the bottom surface of the sand basin may be set in consideration of the amount of sediment deposited between the intersection of the nozzle injection center line and the bottom surface of the sand basin to the side wall.

  The nozzle installed in the vicinity of the side wall of the sand basin is composed of a straight base tube, a 45 ° elbow, and a nozzle head, and one end of the 45 ° elbow is coupled to the tip of the base tube by screwing, It is desirable that the base end of the nozzle head is screwed to the other end of the 45 ° elbow.

  According to the present invention, the water sprayed from the nozzle and landed on the bottom surface of the sand basin diverts into the trough direction and the side wall direction on the bottom surface. The sediment that has accumulated in between is washed away. The momentum of the water flowing in the direction of the side wall is small, but the water diverted in the direction of the trough has an extremely large momentum of the water flow because the bottom surface of the sand basin is inclined in the direction of the trough. Therefore, the earth and sand flowing from between the side wall and the jet swimsuit point by the water diverted in the side wall direction can smoothly flow into the trough by obtaining the momentum of the water flow diverted in the trough direction downstream from the jet swimsuit point. . Therefore, the earth and sand deposited on the bottom surface of the sand basin are collected in the sand collecting pit without remaining, so that the sand collecting efficiency is improved.

  Further, according to the present invention, the water from the nozzle flows from the upper end of the bottom surface of the sand basin to the entire bottom surface thereof, so that the earth and sand accumulated on the bottom surface of the sand basin are all flowed without remaining, Collected in the sand collection pit.

It is a longitudinal cross-sectional view of the rainwater treatment facility including a sand basin. FIG. 2 is a partially omitted plan view of the range of line XX in FIG. 1. FIG. 3 is a cross-sectional view taken along line Y1-Y1 of FIG. FIG. 3 is a sectional view taken along line Y2-Y2 of FIG. FIG. 3 is a cross-sectional view taken along line Y3-Y3 of FIG. It is a water supply system diagram. It is a front view of a nozzle header. It is a figure which shows the attachment state with respect to the sand basin of a nozzle header. It is a figure explaining the attachment angle with respect to the sand basin bottom face of the nozzle of the nozzle header. It is a figure explaining the control apparatus of a sand collecting apparatus. It is explanatory drawing of a water level sensor. It is a flowchart figure of a sand pump control means. It is a flowchart figure of a switching valve control means. It is a figure which shows the attachment state of the nozzle header which concerns on other embodiment of this invention. It is a figure which shows the attachment state of the nozzle header in the conventional sand collecting apparatus.

Next, embodiments of the present invention will be described with reference to the drawings.
In FIG. 1, reference numeral 1 denotes a rainwater treatment facility, which includes a sand basin 2 and a pump well 3 formed between side walls Wa and Wb (see FIG. 2). The settling basin 2 is connected to an inflow trough 4 from which sewage such as rainwater and sewage is collected from a sewage pipe not shown. A dam device 5 is installed at the downstream end of the inflow dredge 4 to allow or block the inflow of sewage from the inflow dredge 4 to the sand basin 2. A contaminant capturing screen 6 is installed immediately before the upstream end.

  As described above, the bottom surface 2a of the sand basin 2 is inclined so that the center is the deepest, and a sand collection pit 7 is formed at the center, and at the bottom of the sand basin, The main trough 8a is formed between the side walls Wa and Wb so that the sand collecting pit side is deep in parallel with the water flow direction in the sand basin, and the surface is inclined downward from the lower end portions of the side walls Wa and Wb to the sand collecting pit 7 (hereinafter referred to as the sand collecting pit 7). 8b is formed, and a number of small troughs 8c extending in the direction perpendicular to the water flow direction in the sand basin from the vicinity of the side walls Wa and Wb to the main trough 8a are formed on the bottom surface of the sand basin. ing.

  Moreover, in order to reduce the burden of the water supply pump P2 and the sand pump P3 which will be described later, the bottom surface of the sand basin is divided into a plurality of regions in the direction of the water flow in the sand basin on both sides of the main trough 8a. In the example of FIG.2 and FIG.8, it divides into 8 area | regions B1-B8. Depending on the size or width of the sand basin, the main trough 8a may be formed at a position near one side wall.

  In addition, nozzles 9a are installed at the upper ends of the main trough 8a and the sand collecting pit inclined surface 8b, and a number of nozzles 9b are installed along the side walls Wa and Wb of the regions B1 to B8. Further, a nozzle 9 c for stirring the collected earth and sand is installed in the sand collecting pit 7.

  A plurality of nozzles 9b installed in the regions B1 to B8 are attached at equal intervals to the nozzle header NH installed in the vicinity of the side walls Wa and Wb of the regions B1 to B8. FIG. 7 shows an example of a nozzle header NH configured by attaching eight nozzles 9b at equal intervals of 500 mm to a mother pipe 11 having a length of 4200 mm having the branch pipe 10. As an example, the pressure of water sprayed from one nozzle 9b is 0.005 MPa, and the discharge rate is 150 liters / minute.

8 and 9, when the bottom surface 2a of the sand basin is inclined by a predetermined angle with respect to the horizontal plane on the main trough side, that is, the inclination angle of the bottom surface 2a with respect to the horizontal plane is θ0, as shown in FIGS. In this case, the incident angle θ1 of the nozzle 9b with respect to the bottom surface of the sand basin, that is, the angle of the spray center line CL with respect to the bottom surface 2a of the sand basin W side is 0.15 to 0.3 m ^3. / Min, it is installed to be in the range of 45-60 degrees. When the incident angle θ1 is set within this range, the water sprayed from the nozzle and landing on the bottom surface of the sand basin can be diverted into the trough direction and the side wall direction on the bottom surface, and injected by the water diverted in the side wall direction. The sediment deposited between the swimsuit point and the side wall flows, merges with the water diverted in the trough direction, and can flow into the trough together with the sediment accumulated between the spray swimsuit point and the trough. In this case, when all of the water sprayed from the nozzle is sprayed in the side wall direction, the bottom surface of the sand basin is inclined in the trough direction. Will lose momentum. However, in the present invention, the water that is diverted in the trough direction and the side wall direction and the water diverted in the trough direction has a remarkably large momentum of the water flow because the bottom surface of the sand basin is inclined in the trough direction. Therefore, the earth and sand flowing from between the side wall and the jet swimsuit point by the water diverted in the side wall direction can smoothly flow into the trough by obtaining the momentum of the water flow diverted in the trough direction downstream from the jet swimsuit point. .

  As described above, the flow rate in the trough direction increases and the flow rate in the side wall direction decreases as the incident angle θ1 is smaller. On the contrary, as the incident angle θ1 is larger, the flow rate in the trough direction decreases and the flow rate in the sidewall direction increases. Therefore, the incident angle θ1 with respect to the bottom of the settling basin of the nozzle may be set in consideration of the amount of sediment deposited between the intersection of the nozzle injection center line and the bottom of the settling basin to the side wall.

  In order to enhance the effect of removing sediment deposited between the landing point LP and the side wall W with respect to the bottom surface of the jet water, it is preferable to make the landing point LP as close to the side wall W as possible. In order to meet the demand to make the landing point LP as close to the side wall W as possible while satisfying the condition that the incident angle θ1 with respect to the bottom surface 2a of the jet water is within the range of 30 to 60 degrees as described above, the present invention In the preferred embodiment, a nozzle 9b having a specific structure as shown in FIG. 9 is used.

  That is, the nozzle 9b is composed of a straight base tube (A), a 45 degree elbow (B), and a nozzle head (C), and one end of the 45 degree elbow (B) is a base tube (I). ) And the other end are connected to the base end of the nozzle head (c) by screwing.

  The reason for using the 45-degree elbow (b) and the nozzle head (c) coupled by screwing is that the nozzle head (c) used in the present invention has a caliber depending on the discharge pressure of the water supply pump or the discharge speed required of the nozzle head. Alternatively, it may be necessary to change to a different mouth shape, so that the exchange is possible. Therefore, according to this embodiment, even when the spraying conditions are different, efficient sand collection can be achieved by simply replacing the nozzle head (c) without leaving soil on the side wall of the bottom surface of the sand basin. Can be realized.

  Then, the central axis CL ′ of the base tube A of the nozzle 9b is displaced by a predetermined angle (θ2) toward the side wall W with respect to the vertical line PL passing through the center O from the mother tube 11, and the injection center of the nozzle head (c) The line CL is displaced by a predetermined angle (θ1) with respect to the sand basin bottom surface 2a.

In the embodiment, θ2 is 15 degrees and θ3 is 45 degrees. Since the inclination angle θ0 with respect to the horizontal plane of the bottom surface 2a of the sand basin is 30 degrees or less, preferably 5 to 15 degrees, it is possible to ensure the incident angle θ1 with respect to the bottom surface 2a of the jetting water in the range of 30 to 60 degrees. In addition, by using a combined body of the base tube (A), the 45-degree elbow (B), and the nozzle head (C), it is possible to make the landing point of the jet water as close as possible to the side wall W side. ing.
The preferable range of the incident angle θ1 with respect to the bottom of the sand basin 2a of jet water is 30 to 60 degrees, and the optimal range is 45 to 50 degrees.

  The side wall W when the distance D from the inner surface of the side wall Wa to the center of the mother pipe 11 is 175 mm, and the vertical line distance X from the tip of the nozzle head (c) to the landing point LP of the jet water is 150 to 350 mm. The horizontal distance Y from the jet water landing point LP is about 400 mm.

  In the pump well 3, a drainage pump P 1 and a water supply pump P 2 that also serves as a staying water pump are installed, and a sand pump P 3 is installed in the sand collecting pit 7. F of FIG. 1 is a filter installed at the downstream end of the sand basin 2.

As illustrated in FIGS. 5 and 6, the switching constituted by an electromagnetic valve for supplying water from the water supply pump P <b> 2 of the pump well 3 to the nozzles 9 a, 9 b, 9 c and stopping the supply. Valve groups VG1, VG2, that is, a trough nozzle switching valve Va, a nozzle header switching valve Vb, and an earth and sand agitation nozzle switching valve Vc are provided. These switching valves Va, Vb1 to Vb8, and the stirring nozzle switching valve Vc are configured to be switched to a water flow state or a water stop state in a predetermined order by a switching valve control means described later.
Relief means 12 is provided via a switching valve Vd in the pipeline connecting the water supply pump P2 and the switching valve groups VG1 and VG2, and water from the water supply pump P2 when all the switching valves are closed is supplied. It is configured to escape to the sand basin 2.

  As shown in FIG. 10, an operation panel 101 having a sand removal start button (not shown) is added to the control device 100 provided in the sand collecting / sand removing device according to the above embodiment, and a drain pump The control means PCON1, the feed water pump control means PCON2, and the sand pump control means PCON3 are incorporated, and the switching valve control means VCON is incorporated. As will be described later, the switching valve control means VCON gives a control signal for driving the group of switching valves Va, Vb, Vc, Vd to open or close in a predetermined order.

  Further, the control device 100 is installed in the sand collecting pit 7, and the water level in the sand collecting pit 7 is higher than a predetermined high water level HWL conceptually shown in FIG. 11, any of the intermediate water level MWL and the low water level LWL. A water level sensor 13 that detects and outputs whether or not there is an electrical connection is electrically connected.

  Then, the effect | action by the said structure is demonstrated about the case where the area | region of a sand basin is four. When the dam device 5 is opened, the sewage flows into the sand basin 2 and further into the pump well 3, and when the water level reaches a predetermined height, the drain pump control means of the control device 100 of the sand removal device. The drain pump P1 provided in the pump well 3 is operated by PCON1, and the water in the pump well 3 is pumped up and transferred to the first settling basin (not shown).

  During the transfer, earth and sand are precipitated from the sewage mixed with the earth and sand flowing into the sand basin 2 and deposited on the bottom surface 2a of the sand basin. When the accumulation amount reaches a predetermined value, the dam device 5 is closed and the inflow of sewage into the sand basin 2 is prevented. When the water level of the settling basin 2 and the pump well 3 is lowered by drainage by the drainage pump P1 and reaches a predetermined water level (WL in FIG. 1), the drainage pump control means PCON1 stops the operation of the drainage pump P1.

  When it is detected that the water level of the pump well 3 has reached a predetermined water level (WL in FIG. 1), the control device 100 activates the feed water pump control means PCON2, the sand pump control means PCON3 and the switching valve control means VCON.

  As shown in FIG. 12, the sand pump control means PCON3 starts the automatic operation mode of the sand pump P3 (S11), and the water level in the sand collecting pit 7 is set to a predetermined high water level by the detection signal from the water level sensor 13. It is checked whether or not it is equal to or higher than HWL (S12), and when it is equal to or higher than the high water level HWL, operation of the sand pump P3 is started (S13).

  Further, as shown in FIG. 13, the switching valve control means VCON first opens the relief valve switching valve Vd to prepare for driving the water supply pump P2 (step S21 in FIG. 13). Subsequently, the trough nozzle switching valve Va is opened (S22), and then the relief switching valve Vd is closed (S23), so that water from the water supply pump P2 flows from the nozzle 9a to the main trough 8a and the sand collecting pit inclined surface 8b. Erupted. Thereby, the earth and sand in each trough is poured toward the sand collection pit 7 with water.

  Since the discharge amount of the sand pump P3 is larger than the discharge amount of the water supply pump P2, the water level in the sand collecting pit 7 is lowered. When the water level sensor 13 detects that the water surface has reached a predetermined intermediate water level (Y in S24), the switching valve control means VCON opens the nozzle header switching valve Vb1 in the first region B1 (S25). Therefore, water is jetted from each nozzle of the nozzle header, and the earth and sand accumulated in the first region B1 is caused to flow toward the main trough and further flows into the sand collecting pit 7. Thus, the sewage mixed with the earth and sand collected and stirred in the sand collecting pit 7 is pumped up by the sand pump P3 and transferred to the sewage settling basin. Thereby, although the water surface in the sand collection pit 7 rises temporarily, it falls in time.

  When the water level sensor 13 detects that the water surface has again reached the predetermined intermediate water level (Y in S26), the switching valve control means VCON closes the nozzle header switching valve Vb1 in the first region B1. In order to open the nozzle header switching valve Vb2 in the second region B2 (S27), water is sprayed from each nozzle of the nozzle header, and the earth and sand accumulated in the second region B2 flows toward the main trough 8a. And then flows into the sand collecting pit 7.

  Therefore, as in the case of the first region, the water level in the sand collecting pit 7 temporarily rises but then decreases, so when the water level reaches a predetermined intermediate water level (Y in S28), The switching valve control means VCON closes the nozzle header switching valve Vb2 in the next second region B2, and further opens the nozzle header switching valve Vb3 in the next third region B3 (S29). Water is jetted from each nozzle.

  Accordingly, as in the case of the first region, the water level in the sand collecting pit 7 temporarily rises but then decreases, so when the water level reaches a predetermined intermediate water level (Y in S210), The switching valve control means VCON closes the nozzle header switching valve Vb3 in the third region B3 and opens the nozzle header switching valve Vb4 in the fourth region B4 (S211), so that water is injected from each nozzle of the nozzle header. Is done.

  Therefore, as in the case of the first region, the water surface in the sand collecting pit 7 temporarily rises but then decreases, so when the water surface reaches a predetermined intermediate water level (Y in S212), The switching valve control means VCON determines that the water injection to the fourth area B4, that is, the last area has ended, opens the relief valve switching valve Vd, and switches the nozzle header switching valve Vb4 in the fourth area B4. Is performed to complete a series of switching valve controls. Also, the feed water pump control means PCON2 stops the operation of the feed water pump P2.

  On the other hand, the sand pump control means PCON3 constantly monitors the detection state of the water level sensor 13 from the start of the operation of the sand pump P3, and by closing the nozzle header switching valve Vb4 in the fourth region B4, Since the water level in the sand pit 7 falls to the low water level LWL (when S14 is Y), the operation of the sand pump P3 is stopped (S15). Thereafter, the sand pump control means PCON3 checks whether or not the control of the switching valve has been completed (S16). If it has not been completed, the process returns to step S12, and the water level becomes high (when S12 is Y). Starts the operation of the sand pump P3 again, but after confirming the completion of the switching valve control (Y in S16), cancels the automatic operation mode of the sand pump (S16).

  As described above, when starting the automatic operation mode, the sand pump P3 is automatically activated when the water level in the sand collection pit is above a predetermined high water level HWL in order to maintain the sand collection pit 7 in a drained state. When the water level drops to a predetermined low water level LWL, the operation is automatically stopped. However, in the method of the present invention, the water level in the sand collection pit is changed to a predetermined high water level HWL and a predetermined level. When the water level drops to the intermediate water level MWL between the low water levels LWL, the nozzle header switching valve in the first order region is closed and the nozzle header switching valve in the second order region is opened. In the meantime, the water level in the sand collection pit is due to the stop of water injection by the closing operation of the nozzle header switching valve in the first order region, the pumping of the sand pump, and the opening operation of the nozzle header switching valve in the second order region. Open water jet By will vary, it may be set to a height position where the water surface is not reduced to a predetermined low water level Atsumarisuna pit between the intermediate level switching operation of the switching valve as a temporal reference for the switching operation of the switching valve. The height position can be calculated from the injection amount of each trough nozzle and each nozzle header, the sectional area of the sand collecting pond, the discharge amount of the sand pump, and the like.

  As shown in FIG. 9, the nozzle 9b of the nozzle header in any of the above regions is attached so that the incident angle θ1 with respect to the bottom of the settling basin of the nozzle is in the range of 30 to 60 degrees. The jet water diverts from the landing point on the bottom of the sand basin to the trough and side walls, and the water diverted to the side wall causes the earth and sand accumulated on the bottom surface from the landing point to the side walls to flow and divert in the trough direction. It joins with water, and the earth and sand accumulated on the bottom surface between the landing point and the trough are poured into the trough. Therefore, all the earth and sand deposited on the bottom surface of the sand basin flows into the trough without remaining, and is collected from the trough into the sand collecting pit 7.

  In the embodiment shown in FIG. 14, the nozzle 9 b ′ of the nozzle header is attached so that the water discharged from the nozzle lands at or near the connection portion C between the bottom surface 2 a of the sand basin and the side wall W. is there.

  In other words, the nozzle 9b ′ has the same configuration as the nozzle 9b shown in FIG. 9, and its injection center line CL is the connecting portion C between the bottom surface 2a of the sand basin and the side wall W, that of the bottom surface 2a of the sand basin. It is attached so as to cross a position very close to the connection part C or a position very close to the connection part C of the side wall W.

  Even when the nozzle 9b ′ is mounted in any of the above modes, the water discharged from the nozzle 9b ′ causes the earth and sand accumulated on the entire bottom surface to flow from the upper end of the bottom surface 2a of the sand basin. There is nothing to do.

  When the nozzle 9b 'is mounted so that the spray center line CL of the nozzle 9b' crosses the position very close to the connection portion C of the bottom surface 2a of the sand basin, a part of the water that lands on the bottom surface is diverted in the direction of the trough 8a. Most of the water is diverted in the direction of the side wall W and immediately rebounded in the direction of the trough 8a by the side wall W. However, since it collides with the water in the direction of the side wall W, the force for flowing earth and sand on the bottom surface 2a is reduced.

  On the other hand, when the nozzle 9b 'is mounted so that the spray center line CL intersects the position C very close to the connection portion C of the side wall W, all of the water landing on the side wall W is connected to the bottom surface 2a of the sand basin Since it is rebounded toward the position close to C, the power loss from the nozzle can be minimized, and it can flow from the entire surface of the bottom surface 2a of the sand basin to the trough 8a without leaving any sediment.

DESCRIPTION OF SYMBOLS 1 Rainwater treatment facility 2 Sand basin 3 Pump well 4 Inflow trough 5 Dam device 7 Sand collection pit P1 Drainage pump P2 Water supply pump P3 Sand pump 8a Main trough 8b Sand collection pit slant surface 8c Small trough 9a Trough nozzle NH Nozzle header 9b , 9b 'Nozzle of nozzle header 9c Stirring nozzle

Claims (1)

  In a sand collection method for a sand basin, in which low pressure water is jetted from a nozzle and the earth and sand accumulated on the bottom of the sand basin is passed through a trough provided at the bottom of the sand basin, the nozzle is installed near the side wall of the sand basin. The incident angle with respect to the bottom surface is jetted to the bottom surface of the sand basin in the range of 30 to 60 degrees, and the water that has landed on the bottom surface is shunted in the trough direction and the side wall direction on the bottom surface, and the water shunted in the side wall direction The earth and sand accumulated between the jet swimsuit point and the side wall are merged with the water diverted in the trough direction, and flow into the trough together with the earth and sand accumulated between the jet swimsuit point and the trough. A sand collection method for sand basins.

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